Since development of gallium nitride (GaN)-based light emitting diodes (LEDs), the GaN-based LEDs are used in various application ranges including natural color LED display devices, LED traffic signboards, white LEDs, and the like.
Generally, a GaN-based LED is formed by growing epitaxial layers on a substrate such as a sapphire substrate, and includes an N-type semiconductor layer, a P-type semiconductor layer and an active layer interposed therebetween. An N-electrode pad is formed on the N-type semiconductor layer and a P-electrode pad is formed on the P-type semiconductor layer. The light emitting diode is electrically connected to an external power source through the electrode pads. In operation, current flows from the P-electrode pad to the N-electrode pad through the semiconductor layers.